Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.56	6.746%	$168.189	$168.19	$168.20	$168.20
Purchase #2	$54.29	6.632%	$57.8905	$57.89	$57.90	$57.90
Purchase #3	$59.96	3.872%	$62.2817	$62.28	$62.30	$62.30
Purchase #4	$235.89	11.374%	$262.7201	$262.72	$262.70	$262.70
Purchase #5	$75.42	5.332%	$79.4414	$79.44	$79.45	$79.40
Purchase #6	$175.39	10.649%	$194.0673	$194.07	$194.05	$194.10
Purchase #7	$166.89	10.477%	$184.3751	$184.38	$184.40	$184.40
7 purchase totals =	$925.40		$1,008.9651	$1,008.97	$1,009.00	$1,009.00